1. Field of the Invention
The present invention relates generally to an electrophotographic type image forming apparatus, such as a copying machine or a printer, and more particularly, to a cleaning apparatus adapted to clean off toner in an image forming apparatus by an electrostatic fur brush.
2. Description of the Related Art
Hitherto, there has been a tandem type color electrophotographic image forming apparatus adapted to primarily transfer a toner image formed on a photosensitive drum, which is a first image bearing member, to an intermediate transfer member in sequence, and then secondarily transfer a toner image, which is a superimposed color image, onto a recording medium.
In this type of color electrophotographic image forming apparatus, the transfer residual toner remaining on an intermediate transfer belt 31, which is an intermediate transfer member, after the secondary transfer is removed by a cleaning apparatus 95 for the intermediate transfer belt 31, as illustrated in FIG. 7A. Thus, the surface of the intermediate transfer belt is cleaned to prepare for the next image transfer. The cleaning apparatus 95 is a cleaning apparatus which has a cleaning blade 107 to scrape off the transfer residual toner from the surface of the intermediate transfer belt 31.
However, it has been impossible to accomplish adequate cleaning off of the toner on a second image bearing member, such as an intermediate transfer belt, by merely mechanically scraping off the toner by the cleaning apparatus. There has been a method, in which a bias having the polarity opposite from the polarity of a toner is applied to a fur brush 90 illustrated in FIG. 7B thereby to electrostatically adsorb the residual toner. However, toners of various charging characteristics remain on the intermediate transfer belt 31, so that it has been difficult to clean all of them by the aforesaid method.
A configuration of a cleaning apparatus for an intermediate transfer belt has been proposed in Japanese Patent Application Laid-Open No. 2002-207403, in which two fur brushes are provided and biases of different polarities are applied thereto. More specifically, as illustrated in FIG. 6, according to an intermediate transfer member cleaning apparatus 36A, each of two fur brushes 90 and 91 is subjected to a different bias so as to cause toners having various charging properties to adsorb to the brushes 90 and 91, respectively, thereby removing the toners from an intermediate transfer belt 31. Referring to FIG. 6, S denotes the outflow path of scattering toners.
As described above, the configuration according to Japanese Patent Application Laid-Open No. 2002-207403 is capable of providing satisfactory cleaning performance. However, as compared with the configuration in which toners are mechanically removed by a blade or the like, the scattering toners tend to flow out toward the downstream side in the moving direction of the intermediate transfer belt 31, as indicated by the dashed arrow. This is because the air flow caused by the rotations of the intermediate transfer belt 31 and the fur brush 91 inconveniently scatters the toners into a space L out from the cleaning apparatus 36A. Further, the toners are also scattered out of the cleaning apparatus 36A due to a decreased outer diameter of the fur brush 91 as the fur brush 91 wears off with time. This leads to defective images or the like attributable to a dirty interior of the apparatus.
The above description relates to an intermediate transfer member carrying toners. The same problem as that described above also applies to a cleaning apparatus for an image bearing member, such as a photosensitive drum carrying toners in the same manner.